/*
 * Author  : Pallab
 * Program : 2757.cxx
 * 
 * Tue Jul 17 15:02:30 2012
 *
 * I have not failed, I have just found 10000 ways that won't work.
 *
 */
 
#include <iostream>
#include <algorithm>
#include <vector>
#include <sstream>
#include <fstream>
#include <string>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <functional>
#include <bitset>
#include <iomanip>

#include <ctime>
#include <cassert>
#include <cstdio>
#include <cmath>
#include <cstring>
#include <climits>
#include <cstdlib>

using namespace std;


#define foR(i1,st,ed) for(int i1 = st , j1 = ed ; i1 < j1 ; ++i1 )
#define fo(i1,ed) foR( i1 , 0 , ed )
#define foE(i1,st,ed) foR( i1, st, ed+1 )
#define foit(i, x) for (typeof((x).begin()) i = (x).begin(); i != (x).end(); i++)
#define bip system("pause")
#define Int int
#define pb push_back
#define SZ(X) (int)(X).size()
#define LN(X) (int)(X).length()
#define mk make_pair
#define SET( ARRAY , VALUE ) memset( ARRAY , VALUE , sizeof(ARRAY) )
#define line putchar('\n')

template<class T1>
inline void debug(T1 _x) {
    cout<<_x<<'\n';
}
template<class T1, class T2>
inline void debug(T1 _x,T2 _y) {
    cout<<_x<<' '<<_y<<'\n';
}
template<class T1, class T2, class T3>
inline void debug(T1 _x,T2 _y,T3 _z) {
    cout<<_x<<' '<<_y<<' '<<_z<<'\n';
}
template<class T1, class T2, class T3, class T4>
inline void debug(T1 _x,T2 _y,T3 _z,T4 _zz) {
    cout<<_x<<' '<<_y<<' '<<_z<<' '<<_zz<<'\n';
}
template< class T1>
inline void debug(T1 _array,int _size) {
    cout<<"[";
    for (int i=0; i<_size; ++i) {
        cout<<' '<<_array[i];
    }
    puts(" ]");
}

inline bool CI(int &_x) {
    return scanf("%d",&_x)==1;
}
inline bool CI(int &_x, int &_y) {
    return CI(_x)&&CI(_y) ;
}
inline bool CI(int &_x, int &_y, int &_z) {
    return CI(_x)&&CI(_y)&&CI(_z) ;
}
inline bool CI(int &_x, int &_y, int &_z, int &_zz) {
    return CI(_x)&&CI(_y)&&CI(_z)&&CI(_zz) ;
}
inline void wait( double seconds ) {
    double endtime = clock()+( seconds* CLOCKS_PER_SEC );
    while ( clock() < endtime ) {
        ;
    }
}

//**********************************************
const int inf = (int)10005;
Int parent[ inf+10 ];

inline void _Make(){
    int i;
    for(i=0;i<inf;++i){
        parent[i]=i;
    }
}
inline Int _Find(Int now_node){
    
    if( now_node != parent[ now_node ] ){
        parent[ now_node ] = _Find(  parent[now_node] );
    }
return parent[ now_node ];
}


//**********************************************

int N;
struct NODE{
	int p;
	int t;
	NODE( int p=0, int t =0):
	p(p),t(t){;}
};
inline bool cmp( NODE A, NODE B){
	return A.p > B.p;
}
NODE vi[10005];


inline void read(){
	fo(i,N){
		CI( vi[i].p, vi[i].t);
	}
}

inline void proc(){
	sort(vi, vi+N, cmp);
	_Make();
	int ret=0;
	fo(i,N){
		int rt = _Find( vi[i].t );
		if( rt>0 ){
			ret+= vi[i].p;
			parent[rt]= _Find(rt)-1;
		}
	}
	cout<<ret<<'\n';
	
}

//#define IO
int main(){
	#ifdef IO
		freopen("2757.in","rt",stdin);
	#endif	
	
	while( scanf("%d",&N)	==1 ){
		read();
		proc();
	}
	
return 0;
}
